This invention relates to a tappet arrangement for an engine valve train and more particularly to an improved valve actuating construction for an internal combustion engine.
It has been recognized that the specific output of an internal combustion engine of a given displacement can be increased through the use of multiple valves for each combustion chamber. For this reason, many high performance engines now employ four valves (two intake and two exhaust) per cylinder of the engine. There are certain advantages that can be enjoyed by further increasing the number of valves. Obviously, however, there is a practical limit to the number of valves that can be used for a single combustion chamber. One of the limiting factors is the geometry of the valves and their actuating mechanism. That is, it is a common practice to operate the valves by overhead camshafts through the media of thimble tappets. However, as the number of valves is increased, the diameter of the thimble tappets that can be employed must be reduced and this reduces the bearing surface for the thimble tappets, which can present further problems.
It is, therefore, a principal object of this invention to provide an improved tappet arrangement for an engine valve train.
It is a further object of this invention to provide a tappet arrangement for an engine valve train that permits the use of a greater number of valves than previously proposed without sacrificing the bearing surface of the individual tappets.
When an engine is provided with a plurality of adjacent thimble tappers each of which operates a respective poppet valve, certain manufacturing difficulties may arise in conjunction with the formation of the openings in the body of the engine that slidably support the thimble tappets. This is particularly true if the thimble tappet has a cross-sectional configuration that is other than circular.
It is, therefore, a still further object of this invention to provide an improved arrangement for slidably supporting a plurality of thimble tappets in an engine body.
It is another object of this invention to provide a sliding support for a plurality of thimble tappets that may be conveniently and easily formed.